Exoskeletons, orthoses and prostheses are intended to enhance human function, often in the context of locomotory motion. Exoskeletons, for example, are worn on the body exterior, around a biological joint that is the target of an intended function (e.g., knee or hip). Depending on the exact purpose of the device, the mechanical effect of the exoskeleton may be to add, remove or store and release energy. Irrespective of purpose, however, all exchange of energy between a human user and a worn exoskeleton occurs through mechanical interaction between the exoskeleton and the human body. The mechanical interaction imparts force distributions on the soft tissue surrounding the joint and limb segments. Typically, the exoskeleton uses a mechanical joint in parallel with the anatomical joint, which reduces flexibility, or the force distributions are parallel to the axis of the limb (i.e. shear), which may be uncomfortable to the user. This discomfort often disrupts device function and hinders the efficacy of the exoskeleton.
International Application number WO2012/175211 A1, the teachings of which are incorporated herein in their entirety, describes a fully integrated system with artificial joints. Artificial joints generally reduce forces exerted on the human body, but often also greatly constrain motion and flexibility. Known powered exoskeletons are also typically heavy and cumbersome to use.
Conventional exoskeleton and assistive devices usually consist of active actuators, passive mechanical components, and mechanical interfaces. In order to reduce design complexity, limb joints are usually considered as one-to-three degrees of freedom (DOF) joints of multiple single DOF hinge joints in a single plane. However, biological joints are complex and usually rotate with respect to a changing instantaneous center. For example, knee motion may be visualized as rotation of a femur about a series of three-dimensional instantaneous axes rather than a single fixed axis. As a result, a mismatch between limb joint motion and mechanical interface motion typically leads to undesired ligament and muscle length changes and other internal mechanical changes. Those undesired effects contribute to discomfort, as well as to slippage and sluggish interaction with such devices.
Therefore, a need exists for devices, such as exoskeletons, orthoses and prostheses that overcome or minimize the above-referenced problems.